Chemically amplified positive resist composition for EB or EUV lithography and patterning process

Abstract

A chemically amplified positive resist composition for EB or EUV lithography is provided comprising (A) a polymer or a blend of polymers wherein a film of the polymer or polymer blend is insoluble in alkaline developer, but turns soluble under the action of acid, (B) an acid generator, (C) a basic compound, and (D) a solvent. The basic compound (C) is a polymer comprising recurring units bearing a side chain having a secondary or tertiary amine structure as a basic active site and constitutes a part or the entirety of the polymer or polymers as component (A).

The invention claimed is: 
     
       1. A chemically amplified positive resist composition for EB or EUV lithography, comprising
 (A) a polymer or a blend of polymers, at least one polymer having a protective group which is deprotected with an acid so that a film of the polymer or polymer blend is insoluble in alkaline developer, but turns soluble therein under the action of acid, 
 (B) an acid generator capable of generating an acid, 
 (C) a basic compound for inhibiting the action of acid, and 
 (D) a solvent, wherein 
 the basic compound as component (C) is a polymer comprising recurring units of the general formulae (1) and (2) and recurring units of formula (5) and (6) and constitutes at least one polymer as component (A), and 
 the composition may optionally further comprise a compound having a molecular weight of up to 1,000 as component (C) other than the basic compound in polymer form, in an amount of up to 1/20 mole per mole of the acid generator as component (B), 
 
       
         
           
           
               
               
           
         
       
       wherein A is a single bond or a C 1 -C 10  alkylene group which may be separated by an ethereal oxygen atom,
 R 1  is each independently hydrogen or methyl, 
 R 2  is each independently a C 1 -C 6  alkyl group, 
 B 1 , B 2 , and B 3  are each independently a single bond, or a linkage selected from the group consisting of a straight or branched C 1 -C 10  alkylene group which may contain an ethereal oxygen atom, a divalent C 5 -C 10  alicyclic group which may be separated by an ethereal oxygen atom, a divalent C 6 -C 14  aromatic group which may be separated by an ethereal oxygen atom, and combinations comprising at least one of the foregoing, 
 Z 1  and Z 2  are each independently a single bond, —CO—O— or —O—CO—, with the proviso that Z 1  and Z 2  do not form a —O—O— structure when B 1 , B 2 , and B 3  contain an ethereal oxygen atom, and B 3  is not a single bond when Z 2  is —CO—O— or —O—CO—, 
 R 3  and R 4  are each independently hydrogen or a monovalent C 1 -C 10  hydrocarbon group which may contain a heteroatom, with the proviso that R 3  and R 4  are not hydrogen at the same time, R 3  and R 4  may bond together to form a ring with the nitrogen atom to which they are attached, and R 3  and R 4  are a divalent C 2 -C 12  hydrocarbon group which may contain a heteroatom when they form a ring, 
 B 3  may bond with R 3  or R 4  to form a ring with the nitrogen atom to which they are attached, and in this case, the nitrogen-containing ring is a 5 to 7-membered ring which excludes a ring of the structure that a lone pair of the nitrogen atom renders the nitrogen-containing ring aromatic, and the nitrogen-containing ring is not an aromatic ring, 
 a is an integer of 0 to 4, b is a positive integer of 1 to 5, p and q are each independently 0 or 1, t is an integer of 0 to 2, with the proviso that when q=0, the atom in B 1  that bonds with a main chain carbon is an ethereal oxygen atom or a carbon atom forming an aromatic ring, and when q=0 and Z 1  and Z 2  are single bonds, one or more of B 1 , B 2 , and B 3  should contain at least two consecutive carbon atoms originating from an alkylene group, or an aromatic group, 
 
       
         
           
           
               
               
           
         
       
       wherein e is an integer of 0 to 4, and R 7  is each independently a halogen atom, a hydroxyl group, a hydroxyl group protected with an acid labile group, optionally halo-substituted C 2 -C 7  acyloxy group, optionally halo-substituted C 1 -C 6  alkyl group, optionally halo-substituted C 1 -C 6  alkoxy group, or optionally halo-substituted C 2 -C 7  alkoxycarbonyl group,
 said recurring units (1) being contained in a content of at least 45 mol% and said recurring units (5) or (6) being contained in a content of at least 10 mol% in the polymer. 
 
     
     
       2. The resist composition of  claim 1  wherein the basic compound as component (C) is a polymer comprising recurring units of the general formula (3) in addition to the recurring units of formulae (1) and (2), 
       
         
           
           
               
               
           
         
       
       wherein C is a single bond or a C 1 -C 10  alkylene group which may contain an ethereal oxygen atom, R 1  is hydrogen or methyl, R 5  is each independently a C 1 -C 6  alkyl group, X is an acid labile group when d is 1, and X is hydrogen or an acid labile group when d is 2 or 3, with at least one X being an acid labile group, a is an integer of 0 to 4, c is 0 or 1, d is an integer of 1 to 3, s is 0 or 1, and w is an integer of 0 to 2. 
     
     
       3. A pattern forming process comprising the steps of:
 applying the positive resist composition of  claim 1  onto a processable substrate to form a resist film, 
 exposing the film patternwise to EB or EUV radiation, and 
 developing the exposed film with an alkaline developer to form a resist pattern. 
 
     
     
       4. The process of  claim 3  wherein the processable substrate is a photomask blank. 
     
     
       5. The process of  claim 4  wherein the photomask blank comprises a chromium compound at the outermost surface.